Cochleae implants have restored partial hearing to more than 100,000 hearing-impaired people worldwide. As cochlear implant performance continues to improve, more and more patients with residual acoustic hearing are eligible for, and some have received, a cochlear implant. We have identified three groups of implant patients who possess significant residual acoustic hearing: those who have a hearing aid on the contralateral side, those who use combined electro-acoustic stimulation in the same ear, and those who use the implant to suppress tinnitus and may have normal hearing contralaterally. We propose to systematically study the interactions between acoustic and electric hearing in these subjects. Our three specific aims are: 1. To construct an accurate pitch map in electric hearing 2. To measure psychophysical interactions between acoustic and electric stimulation 3. To probe the mechanisms and optimize the performance of bimodal hearing An accurate pitch map will allow us to reconstruct "electric harmonics" and develop authentic acoustic simulations of the cochlear implant. A systematic characterization of the psychophysical interactions is necessary to understand the mechanisms and maximize the benefit of bimodal hearing. The proposed work is of high clinical relevance because it may help overcome two of the most significant shortcomings of the current cochlear implants, namely, music perception and speech recognition with background noise, particularly when the noise is a competing voice.